free-piston gage [eng] An instrument for measuring high fluid pressures in which the pressure is applied to the face of a small piston that can move in a cylinder and the force needed to keep the piston stationary is determined. Also known as piston gage. { ¡frei ¡pis-tsn 'gaij } free port [civ eng] An isolated, enclosed, and policed port in or adjacent to a port of entry, without a resident population. { 'fri .port} free slack See free float. { ¡frei 'slak } free-swelling index [eng] A test for measuring the free-swelling properties of coal; consists of heating 1 gram of pulverized coal in a silica crucible over a gas flame under prescribed conditions to form a coke button, the size and shape of which are then compared with a series of standard profiles numbered 1 to 9 in increasing order of swelling. { 'fri .swel-ig 'in.deks } free turbine [mech eng] In a turbine engine, a turbine wheel that drives the output shaft and is not connected to the shaft driving the compressor. { ¡frei 'tsr-bsn } free vector [mech] A vector whose direction in space is prescribed but whose point of application and line of application are not prescribed. { ¡frei 'vek-tsr } freeze [eng] 1. To permit drilling tools, casing, drivepipe, or drill rods to become lodged in a borehole by reason of caving walls or impaction of sand, mud, or drill cuttings, to the extent that they cannot be pulled out. Also known as bind-seize. 2. To burn in a bit. Also known as burn-in. 3. The premature setting of cement, especially when cement slurry hardens before it can be ejected fully from pumps or drill rods during a borehole cementation operation. 4. The act or process of drilling a borehole by utilizing a drill fluid chilled to minus 30-40°F, (minus 34-40°C) as a means of consolidating, by freezing, the borehole wall materials or core as the drill penetrates a water-saturated formation, such as sand or gravel. {friz } freeze drying [eng] A method of drying materials, such as certain foods, that would be destroyed by the loss of volatile ingredients or by drying temperatures above the freezing point; the material is frozen under high vacuum so that ice or other frozen solvent will quickly sublime and a porous solid remain. {'friz .dri-ig } freezer [mech eng] An insulated unit, compartment, or room in which perishable foods are quick-frozen and stored. { 'freiz-sr } freeze-up [mech eng] Abnormal operation of a refrigerating unit because ice has formed at the expansion device. { 'friz.sp } freezing microtome [eng] A microtome used to cut frozen tissue. {¡friz-ig 'ml-krs.tom }

freight car [eng] A railroad car in or on which freight is transported. {'frat .kar} freighter [eng] A ship or aircraft used mainly for carrying freight. { 'frad-sr} freight ton See ton. { 'frat .tsn } french [mech] A unit of length used to measure small diameters, especially those of fiber optic bundles, equal to 1/3 millimeter. { french } french coupling [des eng] A coupling having both right- and left-handed threads. { ¡french 'ksp-lig }

{¡fri-kwsn-si .kam-psn'sa-shsn } frequency domain [cont sys] Pertaining to a method of analysis, particularly useful for fixed linear systems in which one does not deal with functions of time explicitly, but with their Laplace or Fourier transforms, which are functions of frequency. { 'fri-kwsn-si ds.man } frequency locus [cont sys] The path followed by the frequency transfer function or its inverse, either in the complex plane or on a graph of amplitude against phase angle; used in determining zeros of the describing function. { 'fri-kwsn-si .lo-kss } frequency meter [eng] 1. An instrument for measuring the frequency of an alternating current; the scale is usually graduated in hertz, kilohertz, and megahertz. 2. A device cali-brated to indicate frequency of a radio wave. { 'fri-kwsn-si .mid-sr} frequency-modulated radar [eng] Form of radar in which the radiated wave is frequency modulated, and the returning echo beats with the wave being radiated, thus enabling range to be measured. { 'fri-kwsn-si .maj-s.lad-sd 'ra

frequency-modulation Doppler [eng] Type of radar involving frequency modulation of both carrier and modulation on radial sweep. { 'frei-kwsn-si .maj-s.la-shsn 'dap-lsr} frequency-modulation synthesis [eng acous] A method of synthesizing musical tones which, in its simplest form, is carried out using two digital oscillators, with the output of one adding to the frequency (or phase) control of the other. {¡fri-kwsn-si .ma-js'la-shsn .sin-ths-sss } frequency response [eng] A measure of the effectiveness with which a circuit, device, or system transmits the different frequencies applied to it; it is a phasor whose magnitude is the ratio of the magnitude of the output signal to that of a sine-wave input, and whose phase is that of the output with respect to the input. Also known as amplitude-frequency response; sine-wave response. {'fri-kwsn-si ri.spans } frequency-response curve [eng] A graph showing the magnitude or the phase of the freq-ency response of a device or system as a function

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.